how should i align the axis to the propeller center in this model.so that i can rotate it in animation
You can parent your object to an 'empty' object.


Add an empty object (Shift+A > Empty (choose another display type if necessary)
Parent your object to the empty (first select the object, then the empty and press Ctrl+P




Now the Rotation properties of your object can be animated in the empty referential. In my example, just animate the "Z" component and that's it.